MSU Extension Apples

This is the fourth maturity apple maturity report for 2022. Reports are sent out every week (usually on Wednesdays), following the MSU fruit team apple maturity calls on Wednesday morning. 

This week in the Grand Rapids area, early varieties are being harvested: Premier Honeycrisp, Paula Red, Ginger Gold, and Zestar. Gala, Honeycrisp, and McIntosh are just beginning to show maturity development, but are still a couple of weeks away from harvest. 

Weather over the past week has been mostly warm and dry. Temperatures were slightly warmer than normal with highs in upper 70s to 80s Fahrenheit all week, and overnight lows in the 50s and 60s. As of Aug. 22, the Michigan State University Sparta Enviroweather station has accumulated 3008.7 Degree Days Base 42 F (DD42). This is slightly above average, which is 2862.2 DD42, and approximately five days ahead of normal. Rainfall over the past week was variable. On Tuesday, most weather stations recorded several tenths of an inch. On Saturday accumulation varied between 0.1 and 1.0 inches, with little rainfall in the Sparta area, greater rainfall in Standale, Belding, and Clarksville areas. Soil moisture in most of the Grand Rapids’ area is near normal, and most areas not experiencing drought conditions, according to the US Drought Monitor.  

Expect fair, dry conditions during the day Wednesday, with a storm system moving into the area Wednesday evening. Rainfall accumulation Wednesday night and most of Thursday will likely be less than 0.25 inches. Cool, dry conditions are expected Friday and Saturday. Another chance of rain is expected Sunday and Monday, with more accumulation. Medium range forecasts indicate slightly warmer and wetter conditions than normal. 

How to read maturity tables 

Each week, we test apple varieties that are nearing maturity in the Grand Rapids area. We are reporting average values for several samples for each variety. Maximum and minimum values are included for the highest and lowest individual fruits evaluated for each, to give a full spectrum of the maturity. 

• Predicted apple harvest dates for 2022 from MSU.  
• More information on harvest management tools and timings can be found in this article. 
• Guidelines from MSU to check for apple maturity in your own orchard, including specific pressure and starch recommendations by variety. 
• Predicting apple maturity and starch chart from Cornell University. 
• Starch chart for Honeycrisp Apples developed by Washington State University. 

Ginger Gold (predicted harvest date: August 23) 

Overall, samples taken this week indicate this variety is mature and ready for harvest. The main maturity index is color for this variety. Background color is changing from green to pale yellow or cream, indicating maturity (this is a 1 or a 2 on our color scale, which counts down from green to yellow, from 5 to 1). Some fruit is developing a minimal amount of pink coloring on sun-side of fruit. Pressures are good, some fruit is beginning to get softer. Sugars and flavor are very good. Starch was quite variable with some fruit still showing minimal clearing and others fully cleared. Ethylene was significant in only a small number of fruit, but this variety does not typically produce high ethylene. 

Premier Honeycrisp (predicted harvest date: August 25) 

Fruit tested represents fruit closest to maturity or ‘first pick’ fruit in each block. This variety is expected to harvest about three weeks before standard Honeycrisp strains. First pick is taking place this week in most locations on the Ridge for untreated fruit. Red color and size improved dramatically in most places following the rain and cool nights over the past couple of weeks. Background color is changing in early fruit to light yellow, indicating maturity. Some fruit is still fairly green. Seeds were more brown this week. Pressures are somewhat low, but Honeycrisp is typically not a very firm apple. Ethylene development was also variable, but significant in fruit in all samples collected. 

Wait for acceptable varietal flavor and color to develop before picking. Picking fruit and getting it into the market early seems like an edge but will hurt repeat sales of this strain and standard Honeycrisp.  

Some bitter pit has been observed in a few locations, but this has been primarily in expected, high risk places, including younger trees, high-risk rootstocks, high vigor trees, and large fruit. High bitter pit-risk fruit should be cooled quickly to the recommended 38 F storage temperature, as conditioning will exacerbate bitter pit, and marketed as soon as possible. Fruit intended for longer storage should be pre-conditioned, with recommended conditions of 68 F (room temperature) for five to seven days. 

Wildfire Gala (predicted harvest date: August 20)

This is an early strain of gala, expected to harvest approximately three weeks ahead of standard gala strains, or near Ginger Gold. It is a summer apple with little storage potential. Samples this week showed maturity is at or very near harvest this week. Red color is excellent, many fruit are near full red color. Background color is lightening, look for a change from green to a pale whitish color. On our scale this is a 2 or a 1. Size has been reported as somewhat small for this variety in general, this will be especially true for trees with a heavy crop. Significant ethylene was being produced by fruit in 2 of 5 samples tested, indicating the onset of maturity. Fruit is still quite firm in some locations. Starch is variable, with some fruit still very starchy, others with starch fully cleared. Sugar is lower than ideal, based on samples we collected, but adequate. Be sure to test your individual blocks for exact maturity. From Craig Kahlke, CCE LOF Program: “Exact maturity indices have not been developed yet, but near full red color, with firmness 15-20 pounds, brix 12-14, and SPI averaging 4-6 are my best guesses at this time.”

Gala (predicted harvest date: September 7)

A few early samples of gala were collected for the second time this week, including Pacific, Gale, and Brookfield strains. Fruit is still mostly immature. Size is improving, especially in blocks with a moderate crop load. Red color is variable, generally improving, but very dependent on strain. High-coloring strains such as Brookfield have excellent red color. Background color is still very green. A small amount of ethylene was being produced in two individual fruit we tested this week, and only just over the threshold we use for indicating onset of maturity. Overall, fruit is still very firm (25 or greater lbs of pressure), only a few fruit were lower, bringing down the average a bit. Sugars are still quite low, and starches are just beginning to clear. A couple more weeks are still needed.

Honeycrisp (predicted harvest date: September 15) 

A few early samples of standard Honeycrisp strains were collected this week. Fruit is still mostly immature, with regard to all maturity indicators. Red color and background color are still just beginning to change. Starch is just starting to clear. Note that this variety has an unusual starch staining pattern: it does not clear in the center first and then in the flesh like other varieties, but instead flesh may begin clearing first. WSU developed a separate scale for starch testing in Honeycrisp, using 1-6 scale. However, we are using a 1-8 scale like the SPI index developed for McIntosh, estimating the percentage of clearing. A little ethylene was present in one fruit in our samples this week, but this was most likely an anomaly and not a good indicator for overall maturity in the region. 

McIntosh (predicted harvest date: September 12) 

A few early samples of McIntosh were collected this week. Fruit is still immature. Red color is developing well, although dependent on stain. We tested primarily Linda Macs this week. Ethylene was present in just one fruit, not a good indicator for the overall maturity of the crop in the region. Starch is just beginning to clear and sugars are still quite low.

Apple maturity sampling parameters 

• Ethylene (% fruits with internal ethylene over 0.2 ppm) = indicates when ethylene begins to influence fruit ripening and it cannot be held back easily after this is reached. 
• Color % = the visual percentage of red color from 0 to 100; range is of all fruits tested. Indicates surface area covered in red and intensity of red color. 
• Background color: 5 = Green, 1 = Yellow; range is of all fruits tested. 
• Firmness in pounds pressure = measured with a Güss Fruit Texture Analyzer; range is of all fruits tested. 
• Starch: 1 = all starch, 8 = No starch; range is of all fruits tested. Using Cornell Starch Iodine Index Chart.  
• Starch For Honeycrisp: will typically be rated using the standard Cornell SPI scale (1-8). However, a separate starch chart for Honeycrisp Apples developed by Washington State University (scale 1-6) also exists. 
• Brix = % sugar measured with Atago PAL-1 Pocket Refractometer 

Looking for more? View Michigan State University Extension’s Apple Maturity page for regional reports throughout the state and additional resources.